I did my research and decided I didn't like how low the Blazer tanks hang below the frame, and found a couple of examples of the 52-54 Chevy sedan tanks being used. I bought the Tanks Inc fuel injection-ready 18gal kit from Speedway and got to work.
I must have missed a few fabrication details on the other installs for this tank because I assumed the fill pipe would run over the frame rail. I decided that since this section of the frame really doesn't carry much load that I would run the fill through the frame rail. This avoids having to raise the bed floor and still raises the tank enough to hide it really well behind the bumper.
I temporarily routed the fill through the bed floor - I'm planning to design a hidden filler behind the tail light like a few guys have done here.